1. Field of the Invention
The present invention relates to metal oxide semiconductor (MOS), and particularly to a lateral diffused metal oxide semiconductor (LDMOS) device.
2. Description of Related Art
In the evolution of complementary metal oxide semiconductor (CMOS), lateral diffused MOS (LDMOS) plays a typical role in high voltage applications, for example, power supplies, power managements, telecommunications, automotive electronics, and industrial controls. An LDMOS device typically features a drain region that is lateral-diffused to the region below the poly gate. With the lateral diffused drain region, the electrical field across a gate oxide film is reduced when compared to the conventional MOS device. Thus, higher operation voltage of the LDMOS device is achieved. Detailed structure and characteristics of a typical LDMOS is introduced by HOSSAIN Zia et al., “Field-plate Effects on the Breakdown Voltage of an Integrated High-voltage LDMOS Transistor,” IEEE Proceedings of 2004 International Symposium on Power Semiconductor Devices & ICs, pp. 237-240, Kitakyushu, Japan, May 2004.
However, the electrostatic discharge (ESD) robustness of the LDMOS device is not as good as the conventional MOS devices. As a result, it is difficult for conventional LDMOS devices to meet the conventional ESD industrial standard, human body model 2 kV, and machine model 200V.
Therefore, an improved LDMOS device is needed to address the aforementioned deficiency and inadequacies.